Electrographic recording apparatus having a porous carrier web for electroscopic print powder



Nov. 28, 1967 Y J. P. cAPPs 3,355,743

ELECTROGRAPHIC RECORDING APPARATUS HAVING A POROUS CARRIER WEB FORELECTROSCOPIC PRINT POWDER I Original Filed Jan. 25, 1960 2 Sheets-Sheet1 M ME/W02 5y J HN P CHPPS Nov. 28, 1967 J. P. CAPPS ELECTROGRAPHICRECORDING APPARATUS HAVING A POROUS CARRIER WEB FOR ELECTROSCOPIC PRINTPOWDER 2 Sheets-Sheet 2 Original Filed Jan. 25, 1960 United StatesPatent O 3,355,743 ELECTRDGRAPHIC RECORDING APPARATUS HAVING A POROUSCARRIER WEB FOR ELEEJTRGSCOPIC PRINT POWDER Iohn P. Capps, Newport News,Va, assignor to Minnesota Mining and Manufacturing Company, St. Paul,Minn, a corporation of Delaware Continuation of application Ser. No.4,258, Jan. 25, 1960. This application Nov. 29, 1963, Ser. No. 328,777 5Claims. (Cl. 34674) ABSTRACT OF THE DISCLOSURE Electrographic recordingapparatus having point scanning electrodes forming a print gap, a thinporous carrier web positioned in the print gap, means for driving thecarrier web through the print gap, means for applying print powder tothe carrier web, means for feeding sheet material through the print gap,and means for impressing modulated high voltage signals across thescanning electrodes. Also corresponding electrographic recording process.

This invention relates to electrographic recording apparatus and to amethod for the reproduction of images, impulses or thevlike. In oneaspect it relates to a simple, dry method for the reproduction offacsimile images on ordinary paper. This is a continuation of Ser. No.4,258 filed January 25, 1960, now abandoned.

The image which is transmitted in a facsimile system is scanned, e.g. bya flying spot scanner, in the transmitter, usually by photoelectricmeans, and the resulting image impulses are transmitted by means oftransmission wires or by means of wireless transmission. The imageimpulses are amplified in the receiver and are conducted to a printerdevice comprising scanning electrodes, for example, a printer spiral anda suitably controlled printer bar. The printer spiral and the printerbar are disposed of in the plane of the line to be printed and extendedover the entire width of the printing paper. The term printer line or,briefly, line is used in the following discussion to mean a line thathas been scanned once or, in other words, a printed line that extendsover the effective printing width of the recording paper. Althoughvarious types of scanning electrodes have been used, in conventionalpage-printing facsimile recorders, it is customary to provide acylindrical drum upon which is mounted an exposed helix wire, and a thinmetal printer bar which extends across the full width of the recordingpage or drum. The marking signal fed between the printer bar and thehelix wire is thus available across the whole surface width, and therecording spot consists of the intersection between the printer bar andthe helix wire. The helix containing drum rotates synchronously with thetransmitting scanner so that the spot or point of intersection betweenthe printer bar and helix wire moves along the length of the printerbar, and thus across the page, in unison with the transmitter scanningmotion, with each marking signal increment passing through the recordingpaper at the proper point as the paper is positioned between the printerbar and helix wire, often referred to as horizontal synchonization.Vertical synchronization is provided by moving the recording paper overthe printer bar at the same rate as the transmitters rate of verticalscanning. Such a helix-type page-printing facsimile recorder isdescribed in US. 2,872,276 and US. 2,415,229.

Currently available apparatus for the direct printing of facsimileimages employs in most cases a specially treated or prepared paper, e.g.electrochemically moistened 3,355,743 Patented Nov. 28, 1967 paper,paper which has been color treated by spark dis charge, etc. Such papersare expensive, are often inconvenient to used and occasionally tend tolose their effectiveness upon aging.

Some facsimile recording systems have attempted to use ordinary paper byemploying inks and smoke particles but the problem of cost, smudging,and the cumbersome and complex nature of the apparatus have remainedserious disadvantages. Other systems, such as that described in US.2,879,422, use writing paper, but require a cathode ray tube to developan electrostatic charge thereon and subsequent visible development ofthe image by wellknown electrostatic developing techniques.

It is therefore an object of this invention to provide a simpleapparatus for the reproduction of facsimile images or other electricalimpulse information.

It is a further object of this invention to provide a simple apparatusfor the simultaneous reception and visible reproduction of facsimileimages and other elec-' trical impulse information.

Another object of this invention is to provide a dry process for thesimultaneous reception and visible reproduction of facsimile images andthe like.

Still another object of this invention is to provide an improved methodfor the permanent and instantaneous reproduction of a transmittedfacsimile image on ordinary paper.

Various other objects and advantages will become apparent from theaccompanying description and from the drawings wherein:

FIGURE 1 is a schematic drawing of the electrographic reproductionapparatus or recorder.

FIGURE 2 is a front view of a preferred embodiment of the facsimilereproduction or recording apparatus, taken along line 22 of FIGURE 3.

FIGURE 3 is a cross-sectional view of the apparatus of FIGURE 2approximately along line 3-3.

FIGURE 4 is a perspective view of an alternative embodiment of the helixtype electrodes.

In accordance with my invention the foregoing and other objects areaccomplished by providing, as schematically shown in FIGURE 1, anelectrical impulse recording apparatus having electrodes E and E forminga print gap therebetween, a carrier web C capable of bearingelectroscopic powder positioned in the print gap adjacent one of saidelectrodes, means for driving the carrier web through the print gap andmeans for simultaneously feeding sheet material D, such as ordinarypaper, through the print gap. Electroscopic powder is supplied to thecarrier web C by means such as roll B and powder hopper A.

In accordance with one embodiment of my invention the foregoing andother objects are accomplished by a system wherein a rotatablecylindrical drum containing a helix wire on the periphery thereof ispositioned in an adjustable spaced relationship adjacent to a printerbar aligned parallel to the longitudinal axis of said drum, a continuousmovable carrier web or matrix containing particulate marking material isdisposed between said drum and said printer bar, means are provided foreffecting the rotation of said cylindrical drum at a predeterminedspeed, means are provided both for feeding paper at variouspredetermined speeds between said drum and said printer bar and also forsimultaneously moving said carrier web in juxtaposition with said paperin the direction of and at the speed of said paper, and means areprovided for impressing the high voltage electrical impulsescorresponding to the facsimile or other transmitted signals across theprint gap existing between said printer bar and said helix wire on saiddrum. For purposes of description the print bar and helical wire wounddrum will 3;. be considered illustrative of preferred scanningelectrodes, although other types of electrodes, including fixedelectrodes, can be used.

With reference to the embodiment shown in FIGURES 2 and 3, the imagereproducing apparatu is provided with a support 2 for holding a freelyrotatable roll of paper 1. The paper from roll 1 is passed under paperguide roller 3 and thence across the top surface of metal housing 36.Rotatable drum 4 containing helical wire 5 and printer bar mount 24containing printer bar 25 are similar to the customary type employed inpage-printing facsimile recording. The amplified facsimile impulses areimpressed as varying or modulated high voltages between the printer bar25 and the helical wire 5, the latter being grounded to the metalhousing 36 through the rotatable axis 6 of drum 4 and the ground strip37. End bearings 9 and 10 support shaft 6 of drum 4, which shaft isdriven by. belt drive 8 from motor 7. A belt take-off 11 from drivenshaft supplies power for rubber coated paper advance roller 14.Rubber-faced wheels 29 on axle 30 are connected to metal housing 36 bymeans of movable lever arms 31 and are maintained, through appropriateopenings in the top surface of housing 36, in pressural contact withpaper advance roller 14 by means of springs 32. A continuous carrier webor matrix 21 passes over carrier web supports 26 and 27, over paperadvance roller 14 and carrier web guide rolls 19 and 28. Tension roll 20rides freely on carrier web 21 at the lowest point of its travel andmaintains the desired tension on the web. Print powder is supplied tothe carrier web 21 by means of a felt surfaced dusting roller 17, whichreceives powder from hopper 22 and transfers it to carrier web 21 duringits clockwise rotation about axis 18. Rotation of axis 18 and dustingroller 17 is effected by a belt take-off from paper advance roller 14.Drop pan 23 is disposed beneath the point of contact between the carrierweb and the dusting roller to collect such print powder as may drop fromthe dusting roller during the dusting operation. I

In the operation of the abovedescribed apparatus the paper from roll 1is brought into contact with the top surface of the print powder-bearingcarrier web 21 as it passes over guide roll 28. Both carrier web andpaper, while in juxtaposition with one another, preferably in acontiguous relationship, move over support 2'7, between the printer bar25 and the rotating drum 4, over support 26, and hence between paperadvance roller 14 and compression wheel 29. The driven rotation of paperadvance, roller 14 thus effects and regulates the forward motion of thepaper and the carrier web at a speed synchronized with the verticalscanning rate of the transmitter. As the paper and carrier web passthrough the print gap between printer bar 25 and the rotating drum 4,the amplified electrical impulses or high voltage impulses correspondingto the facsimile signals are impressed between the printer bar and thehelical wire 5, thereby producing an electrostatic field of forcetherebetween. .Such high potentialsand the resulting electrostaticfields cause the particles contained on the carrier web to trans- .ferto the adjacent paper where they are retained both by the electrostaticcharge developed thereon and by the 'ingraining of the particles intothepaper. The width of the print gap is preferably kept at a minimum toprovide highest resolution and definition.

For purposes of this invention the sheet material employed to receivethe print powder may be any ordinary paper, such as sulfite paper or maybe fabric or plastic sheets. However, in order to reduce the danger ofsmearing and smudging or to obviate the necessity for a fixingoperation, a relatively'porous or rough surfaced material is preferred,and paper is most preferred. The continuous carrier web or belt 21 ismade from any relatively thin, flexible material to which the printpowder can be loosely adhered either in the interstices of such porousmaterials as cellulosic and other non-woven mesh or fabric, natural andsynthetic fabrics, paper, etc., or to the surface of such relativelynon-porous materials as synthetic plastic sheets, etc. Generally, porousor rough surfaced materials of minimal thickness are preferred.

Any finely divided electroscopic powder, i.e. a powder capable ofbearing an electrical charge, can be used as the print powder. Selectionof a particular powder naturally is dependent on the color desired. Suchelectroscopic powders as those employed in the xerographic art areparticularly suitable. One preferred powder which produces dense blackmarkings is manganese oxide (MnO Illustrative of other powder materialsare iron oxide (red), chromium oxide (green), and pigments such asultramarine blue, with or without added fillers or carriers. Fillers andcolorants may, of course, be added, and certain materials, such asdiatomaceous clay, can be incorporated into the powder composition toimprove its adherence to the carrier web.

As mentioned earlier, the facsimile impulses are amplified and areimpressed across the print gap between the print bar and rotating drumas a high voltage, the actual operating voltage selected depending onsuch factors as the actual width of the print gap, the porosity of thepaper to be printed, the nature of the carrier web, etc. It has beenfound that the electroscopic print powders, such as manganese oxide, canbe more readily transferred from the carrier web to the paper at a givenstrength of electrostatic field if the field is pulsated rather thanmaintained at a constant potential gradient, although such pulsation isnot essential to obtain the desired result..Generally, pulsating D.C.voltages of the order of magnitude of 5000 to 10,000 volts or higher,preferably above about 10,000 volts, have been found to be satisfactory.

The electrical polarity of the print bar and the helical wire in therotating drum is usually, though not neces sarily, selected with regardto the electroscopic or charge characteristics of the print powder.Hence, for example, when a powder having an electronegative chargeisused as print powder in the above-described apparatus, the helical wireof the rotating drum is preferably positive with respect to the printbar. Some suitable xerographic powders contain a pigmented resin,specially formulated to provide a high electronegative charge in thetriboelectric series and to permit fusing or fixing at a temperaturewhich will not damage the paper, and a beaded carrier which provides ahigh charge at the electropositive end of the triboelectric series.Applicant has found that the metal oxide powders, particularly manganeseoxide, can be used in the above apparatus without regard to therespective polarities of the print bar and the helical wire. It isbelieved that the electroscopic particles in the carrier web assume thecharge of the electrode adjacent to, i.e. in closest proximity to, thecarrier web, are then repelled therefrom and are projected into thepaper, which probably is oppositely charged to some extent by the otherelectrode. In spite of the possible theoretical explanation therefor,any electroscopic powder capable of bearing an electrical charge can beemployed in the instant invention,

and factors such as polarity, Width of the print gap, electricalpotential, etc. can be readily adjusted to produce optimum results.Moreover, provision may be made for precharging the electroscopi cparticles, if desired.

In place of the stationary print bar described above, a rotating drumhaving a helical Wire mounted on the exterior thereof, similar torotating drum 4, can be employed. This helical wire should be woundabout the drum in a direction opposed to that of the wire on drum 4 suchthat it intersects or passes adjacent to the helical wire in drum 4 at asingle point in the print gap, which point moves transversely across thepaper in synchronization with the scanning rate of the transmitter. Suchan embodiment tends to provide a more clearly defined intersectionbetween the electrodes or points of applied electrical potential and toincrease the clarity of the resulting image. This embodiment is shown inFIGURE 4.

The speed of rotation of the helical wire wound drum or drums isadjusted to provide a horizontal scanning rate similar to that of thetransmitter. Such speed can be further regulated by varying the diameterof the drum or by utilizing a helical wire or wires of varying degreesof pitch. When more than one helical wire is wound on the drum the pitchor progression of the wires should be such as to provide only one pointof contact on any longitudinal surface line drawn parallel to the axisof said drum, thereby to permit only one scanning point per line at anygiven time.

The above embodiments of the process and apparatus of this inventionhave been shown and described for purposes of explaining andillustrating the invention, obvious modifications will occur to a personskilled in the art and it is not intended to limit the invention to theexact details shown and described herein.

I claim:

1. In a helix-type page-printing facsimile recorder containing arotatable scanner drum having a helical wire on the periphery thereofand a printer bar disposed in parallel relationship to the axis ofrotation of said drum and forming a print gap therebetween, theimprovement which comprises, in combination, a continuous thin, porouscarrier web positioned in said print gap, said carrier web havinginterstices and being capable of loosely bearing an electroscopic powderin said interstices, means for driving said carrier web through saidprint gap, means for applying print powder to said carrier web beforepassing through said print gap, means for feeding sheet material throughsaid print gap in juxtaposition with said carrier web, and means forimpressing a modulated high voltage potential across said print gap.

2. In an electrographic recording apparatus having point scanningelectrodes forming a print gap therebetween, the improvement whichcomprises, in combination, a thin, porous carrier web having intersticesand being positioned in said print gap, means for driving said carrierweb through said print gap, means for applying print powder onto saidcarrier web and into the interstices thereof before passing through saidprint gap, means for feeding sheet material through said print gap, andmeans for continuously impressing modulated high voltage signalsdirectly across said electrodes.

3. In a facsimile recording apparatus having point scanning electrodesforming a print gap therebetween, the improvement which comprises, incombination, a thin, porous continuous carrier web positioned in saidpn'nt gap adjacent one of said electrodes, said carrier Web havinginterstices and being capable of loosely bearing an electroscopic powderin said interstices, means for driving said carrier web through saidprint gap, means for feeding sheet material through said print gap injuxtaposition with said carrier web, means for applying print powder tosaid carrier web, before passing through said print gap and means forcontinuously impressing high voltage facsimile signals directly acrosssaid scanning electrodes.

4-. In a helix-type page-printing facsimile recorder containing arotatable scanner drum having a helical wire on the periphery thereofand a printer bar disposed in parallel relationship to the axis ofrotation of said drum and forming a print gap therebetween, theimprovement which comprises, in combination, a thin, porous continuouscarrier web having interstices and being positioned in said print gap,means for driving said carrier web through said print gap, means forapplying print powder onto said carrier web and into the intersticesthereof before passing through said print gap, said carrier web beingcapable of loosely bearing an electroscopic powder, means for feedingsheet material through said print gap in juxtaposition with andcontiguous with said carrier web, and means for impressing a pulsatinghigh voltage potential above about 10,000 volts D.C. across said printgap.

5. In a helix-type page-printing facsimile recorder containing arotatable scanner drum having a helical wire on the periphery thereofand a printer bar disposed in parallel relationship to the axis ofrotation of said drum and forming a print gap therebetween, theimprovement which comprises, in combination, a thin, porous continuouscarrier web having interstices and being positioned in said print gap,means for driving said carrier web through said print gap, means forapplying print powder onto said carrier web and into the intersticesthereof before passing through said print gap, said carrier web beingcapable of loosely bearing an electroscopic powder, means for feedingsheet material through said print gap in juxtaposition with andcontiguous with said carrier web, and means for impressing a pulsatinghigh voltage potential above about 10,000 volts D.C. across said printgap.

References Cited UNITED STATES PATENTS 2,817,767 12/ 1957 Rosenthal346--74 2,890,923 6/ 1959 Huebner 34674 2,901,374 8/1959 Gundlach 346742,932,690 4/ 1960 Adams 1786.6

BERNARD KONICK, Primary Examiner. L. I. SCHROEDER, Assistant Examiner.

3. IN A FACSIMILE RECORDING APPARATUS HAVING POINT SCANNING ELECTRODESFORMING A PRINT GAP THEREBETWEEN, THE IMPROVEMENT WHICH COMPRISES, INCOMBINATION, A THIN, POROUS CONTINUOUS CARRIER WEB POSITIONED IN SAIDPRINT GAP ADJACENT ONE OF SAID ELECTRODES, SAID CARRIER WEB HAVINGINTERSTICES AND BEING CAPABLE OF LOOSELY BEARING AN ELECTROSCOPIC POWDERIN SAID INTERSTICES, MEANS FOR DRIVING SAID CARRIER WEB THROUGH SAIDPRINT GAP, MEANS FOR FEEDING SHEET MATERIAL THROUGH SAID PRINT GAP INJUXTAPOSITION WITH SAID CARRIER WEB, MEANS FOR APPLYING PRINT POWDER TOSAID CARRIER WEB, BEFORE PASSING THROUGH SAID PRINT GAP AND MEANS FORCONTINUOUSLY IMPRESSING HIGH VOLTAGE FACSIMILE SIGNALS DIRECTLY ACROSSSAID SCANNING ELECTRODES.